One example of a conventional technique relates to a pair of rotors that are carried on a driving shaft coaxially and integrally with a relief valve that is disposed between the pair of rotors and directed toward the driving shaft in a direction perpendicular thereto. See, for example, Japanese Patent Laid-open No. 2000-199413. If it is necessary to feed oil to the components of a power unit at respective different hydraulic pressures, oil pumps are provided at its discharge sides with relief valves having respective different pressures so that oil may be fed to destinations at respective different hydraulic pressures. However, in such an arrangement described above, the plurality of relief valves project in a direction perpendicular to the driving shaft, which increases the sizes of the oil pumps. Consequently, the oil pumps will largely occupy the layout-based restrictive space in the internal of the power unit.
One example of a conventional oil pump structure that includes a plurality of oil pumps having the same discharge pressure that are integrally combined with each other through a single driving shaft. See, for example, Japanese Patent Laid-open No. 2000-199413, FIG. 3. This example discloses that a plurality of rotors are secured to the driving shaft by means of corresponding connection pins.
If one of the plurality of oil pumps is for high pressure and the other is for low pressure, hydraulic pressures applied to the rotors are different from each other, which leads to different torque for driving the rotors. As the torque is increased, it is necessary to increase the diameter of the rotor connection pin. The increased diameter of the pin requires an enlarged pin insertion hole. Thus, an increased diameter of the driving shaft is required which is likely to increase the weight of the oil pump.
The present invention intends to solve the problem of the conventional technique described above and provide means for arranging a plurality of relief valves in a compact manner, thereby reducing the size of an oil pump assembly.
An embodiment of the present invention provides an oil pump assembly that includes a plurality of pump chambers constituting a plurality of oil pumps, respectively with a plurality of rotors fitted into the pump chambers, respectively. A single driving shaft carries the plurality of rotors to form a single body wherein oil pumped up from an oil pan is supplied under pressure from the plurality of oil pumps to different associated destinations in a power unit. The oil pumps are provided with respective relief valves adapted to pass oil discharged from the corresponding pump chambers therethrough and axes of the relief valves are arranged parallel to the driving shaft.
An embodiment of the present invention provides a discharge port for at least one of the relief valves that is disposed within a width of the rotors as viewed from a direction perpendicular to the driving shaft.
An embodiment of the present invention provides respective discharge ports of the relief valves that are disposed within a width of the rotors as viewed from a direction perpendicular to the driving shaft with the relief valves being arranged to have most portions of the full lengths that overlap each other.
An embodiment of the present invention provides an outer shell of the oil pump assembly that is composed of a pump case body and pump covers shielding lateral sides of the pump cover, the pump chambers are defined between the pump case body and the pump covers to house the rotors in the corresponding pump chambers. The plurality of relief valves are arranged to be inserted in cavities of the pump case body.
An embodiment of the present invention provides for a plurality of relief valves that are disposed between a strainer and the oil pumps as viewed from the lateral side of the power unit.
An embodiment of the present invention provides for the plurality of relief valves that are arranged parallel to each other along an oil stream line of an oil inflow passage extending from the strainer to the oil pumps.
According to an embodiment of the present invention, since the axes of the plurality of relief valves are arranged parallel to the driving shaft, the drive shaft can be brought close to the relief valves, so that the relief valves can be arranged compactly.
According to an embodiment of the present invention, since the discharge port of the relief valve is disposed within the width of the rotor as viewed from a direction perpendicular to the driving shaft, the relief valve can be brought close to the oil pump for a compact arrangement. In addition, the discharge oil passage is brought close to the pump suction port to shorten the relief oil passage, thereby simplifying the oil passages.
According to an embodiment of the present invention, since the respective discharge ports of the relief valves are disposed within the width of the rotors and the relief valves are arranged to have most portions of the full lengths that overlap each other, the plurality of the relief valves can be further arranged in a compact manner. Note that “to have most portions of the full lengths that overlap each other” means that “a plane perpendicular to the axes of the relief valves are shared by most of the portions of the full lengths of the relief valves”.
According to an embodiment of the present invention, since the oil pump assembly is composed of the pump case body and the pump covers shielding both the sides of the pump case body and the plurality of the relief valves are disposed by inserting them into the corresponding cavities of the pump case body, the number of components can be reduced by eliminating members used to support the relief valves.
According to an embodiment of the present invention, since the plurality of relief valves are disposed between the strainer and the oil pump as viewed from the lateral side of the power unit, an unused space between the strainer and the oil pumps is used to dispose the relief valves therein, thereby further reducing the size of the power unit.
According to an embodiment of the present invention, since the plurality of relief valves are arranged along the oil stream line extending from the strainer to the oil pump, the plurality of relief valves can be further arranged compactly while ensuring sufficient oil passages.
The present invention intends to prevent a driving shaft from increasing its diameter particularly for a high pressure pump by changing means for connecting rotors to the driving shaft depending on discharge oil pressures.
According to an embodiment of the present invention, the present invention solves the above problem by providing an oil pump assembly structure including a low pressure oil pump which includes a pump chamber, an outer rotor and an inner rotor that is adapted to pump oil in an oil pan and supply under pressure of the oil to components of a power unit. A high pressure oil pump which includes a pump chamber, an outer rotor and an inner rotor is adapted to pump oil in the oil pan and supply the oil under pressure to the other components of the power unit. A driving shaft is provided on which a plurality of the inner rotors are carried concentrically and integrally. The inner rotor of the low pressure oil pump is secured to the driving shaft by means of a retaining pin in such a manner so as to be unable to rotate with respective to the driving shaft. The inner rotor of the high pressure oil pump is fitted to a portion having a plurality of flat surfaces formed in the vicinity of an end of the driving shaft and is secured to the driving shaft in such a manner so as to be unable to rotate with respect to the driving shaft with the driving shaft being driven by receiving power of an internal combustion engine.
According to an embodiment of the present invention, oil pressurized in the pump chamber is symmetrically discharged from the rotor to both sides of the rotor, interflows and then is discharged from the oil pump.
According to an embodiment of the present invention, a water pump is provided adjacent to the low pressure oil pump of the oil pumps with a driving shaft of the water pump being disposed coaxially with the driving shaft of the oil pumps. A power transmission means is provided which receives power of the internal combustion engine and is located at an end of the oil pump driving shaft on a side of the low pressure oil pump with one of the end of the oil pump driving shaft and an end of the water pump driving shaft being formed in a projecting manner and the other being formed in a recessed manner. Thus, both the pump driving shafts are coupled to each other.
According to an embodiment of the present invention, since the inner rotor of the high pressure oil pump is fitted and secured to a portion having a plurality of flat surfaces formed in the vicinity of an end of the driving shaft, the strength of connection between the inner rotor and the driving shaft can be increased. Thus, it is unnecessary to increase the diameter of the driving shaft, thereby reducing the size of the oil pump. In addition, in the case of a flat surface fitting, not only the length of the flat surface can be set more freely but also the rotor having manufacturing or assembling errors can be attached to the driving shaft more freely in terms of the axial position thereof.
According to an embodiment of the present invention, since the oil that has passed the rotor is symmetrically discharged from the rotor to both the sides of the rotor, the pressure of the oil discharged to both sides provides a rotor-centering effect, which reduces the contact between the rotor and the pump chamber, thereby suppressing frictional resistance therebetween. Accordingly, a load acting on the driving shaft is reduced, so that the diameter of the driving shaft can be reduced.
According to an embodiment of the present invention, the power transmission means is provided at the end of the driving shaft on the side of the low pressure oil pump, the end of the driving shaft of the water pump is disposed coaxially with the end, and both the ends are fitted and coupled to each other. Therefore, a distance between the power transmission means and the projecting-recessed connection portion located at the end of the driving shaft is small, so that torsion acting on the driving shaft is reduced. Accordingly, it is unnecessary to reinforce the projecting-recessed connection portion and reduce the diameter of the driving shaft.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.